Analysis of side ratio effect on propagation of ultrasonic guided waves in a bar with rectangular section

In this research side ratio effect of ultrasonic guided waves in a bar with rectangular cross section is investigated and wave structure is calculated and plotted. The motion of ultrasonic guided waves in the mentioned bar is considered as a three dimensional problem. In the homogenous equation system that is obtained to satisfy stress free surface boundary conditions, the ratios determinant of this system should equal zero. So, the frequency equation is obtained. The real roots of this equation are extracted and frequency spectrum, phase and group velocity diagrams and wave structure for longitudinal, torsional and bending waves are plotted by a written computer program by Matlab. Increasing cross section bar side ratio shows when the frequency increases the longitudinal and torsional waves phase velocity decreases and bending waves phase velocity increases. Also, for some modes replacing particles on the bar surface is considerable and for some others is negligible.